Surface stabilized ferroelectric liquid crystal devices

• US 4,563,059 A
• Filed: 07/07/1983
• Issued: 01/07/1986
• Est. Priority Date: 01/10/1983
• Status: Expired due to Term

• Current Assignee: Clark, Noel A., Sven T. Lagerwall
• Original Assignee: Clark, Noel A., Sven T. Lagerwall
• Inventors: Clark, Noel A., Lagerwall, Sven T.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lewis, David
• Application Number:
  US06/511,733
• Time in Patent Office: 915 Days
• Field of Search: 350/351, 350/350 S, 350/346, 350/340, 350/341, 350/339 R, 350/335
• US Class Current: 349/123
• CPC Class Codes: C09K 19/02 characterised by optical, electrical or physical properties of the components, in general
• CPC Class Codes: C09K 19/0225 Ferroelectric
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

A liquid crystal device including a ferroelectric liquid crystal disposed between plates treated to enforce a particular ferroelectric molecular orientation to the plates. The devices employ along or in combination non-planar boundary conditions, polar boundary conditions, boundaries with multiple physical states, intrinsic spontaneous splay distortion of the polarization orientation field, combined ferroelectric and dielectric torques, layers tilted with respect to the plates. The plates are spaced by a distance sufficiently small to ensure unwinding of the helix typical in a bulk of the material to form either monostable, bistable or multistable states which exhibit novel electro-optic properties. The liquid crystal is responsive to an externally applied electric field, temperature or the like to make a light valve or other electro-optical device.

Claims

1. A liquid crystal device comprising:

a quantity of ferroelectric liquid crystal having a plurality of adjacently disposed layers each comprised of a plurality of molecules, each molecule having a long axis, said molecules of said layers in a bulk of said liquid crystal forming helices having axes perpendicular to said layers; and

first and second means, each transverse to and contiguous with said layers, for containing said liquid crystal, at least said first means aligning the long axes of said molecules adjacent thereto at an angle Ω

(α

) from the normal to said first means, said angle Ω

(α

) being a predetermined function of an angle α

, said angle α

being an angle between a reference vector in a plane parallel to said first means and a projection of said long axes of said molecules onto said plane, the distance between said first and second means being less than the distance at which said helices form in the absence of an electric field, said first and second means causing said long axes to assume one of a plurality of stable orientations.

2. A device as in claim 1 wherein said angle Ω

(α

) is a constant over all of said angles α

.

3. A device as in claim 1 wherein said first and second means are parallel.

4. A device as in claim 1 wherein at least one of said first means and said second means causes said long axes to align at said angle Ω

(α

) which is symmetric with respect to a plane of symmetry perpendicular to said plane within which said angle α

lies.

5. A device as in claim 4 wherein said first and second means include first and second plates, at least said first plate being glass coated with a hydrocarbon layer.

6. A device as in claim 1 further comprising means for applying an electric field to at least a portion of said layers in a direction having a significant component perpendicular to said layers, the strength of said electric field being sufficient to shift said long axes in said portion from one of said stable orientations to another of said stable orientations.

7. A device as in claim 1 wherein said first and second means include first and second plates, at least said first plate being glass coated with a hydrocarbon layer.

8. A device as in claim 1 wherein said first and second means include first and second plates, at least said first plate being glass coated with a hydrocarbon layer having molecules oriented in a predeterminsd manner.

9. A device as in claim 1 wherein said first and second means include first and second plates, at least said first plate being glass having unidirectional surface scratching.

10. A device as in claim 1 wherein said first and second means include at least one surface layer coated with unidirectionally evaporated material.

11. A device as in claim 10 wherein said material is silicon monoxide.

12. A device as in claim 1 wherein said liquid crystal is any one of the group consisting of decycloxybenzylidene p'"'"'-amino 2 methyl butyl cinnamate and hexyloxy-benzylidene p'"'"'-amino 2 chloropropyl cinnamate.

13. A process of making a liquid crystal device including a ferroelectric liquid crystal, molecules, having long axes, in a bulk of said liquid crystal forming helices and first and second means for containing said liquid crystal, said process comprising the steps of:

aligning the molecules of said liquid crystal adjacent to at least said first means at an angle Ω

(α

) from the normal to said first means, said angle Ω

(α

) being a predetermined function of an angle α

, said angle α

being an angle between a reference vector in a plane parallel to said first means and a projection of said long axes of said molecules onto said plane, but free to move between at least two particular orientations; and

suppressing the formation of said helices.

14. A process as in claim 13 wherein said angle Ω

(α

) is a constant over all of said angles α

.

15. A process as in claim 13 wherein said first and second means includes at least one glass plate and said process further comprises the step of bidirectionally scratching the surface of said at least one glass plate.

16. A process as in claim 15 further comprising the step of coating said at least one glass plate with a hydrocarbon layer.

17. A process as in claim 13 wherein said first and second means include at least one glass plate and said process further comprises the step of coating said at least one glass plate with a hydrocarbon layer having molecules oriented in a predetermined manner.

18. A process as in claim 13 wherein said first and second means include at least one glass plate and said process further comprises the step of unidirectionally scratching a surface of said at least one glass plate.

19. A process as in claim 13 further comprising the step of at least one of said first and second means the step of coating at least one of said first and second means with unidirectionally evaporated material.

20. A process as in claim 19 wherein said material is silicon monoxide.

21. A process as in claim 13 wherein said first and second means include at least one glass plate and said method further comprises the step of